1. Field of Invention
The present invention relates to battery units that operate electrical and other small-scale devices. More particularly, the present invention relates to a device and method to seal and mechanically support the connection between a battery terminal and a medical device.
2. Description of the Prior Art
Batteries are commonplace in both everyday life and in scientific fields. As battery technology continues to make great strides, battery sizes have decreased, while battery power has increased. These advances render miniature batteries, particularly lithium ion batteries, indispensable in the field of biomedicine.
Typically, a battery is placed in a case having an opening that exposes the battery terminal. The battery case is then connected to a medical device via the exposed battery terminal. The integrity of the connection between battery case and medical device is critical for proper function and safety.
In one application of this technology, batteries are used in conjunction with medical devices, such as neurological stimulators, that are implanted in a human patient. In such applications, the integrity of the connection between battery and medical device has even further importance. A connection failure may result in medical device malfunction giving rise to potentially devastating results. Accordingly, the connection must not only be mechanically sound, but the connection must also prevent the introduction of foreign matter, such as body fluids and other contaminants, that may compromise the electrical connection.
More particularly, one such application involves the use of cochlear stimulators that allow deaf and near deaf patients to experience the sensation of sound waves through electromechanical stimulation. One type of cochlear stimulator comprises an implantable portion and an external portion that interacts with the implanted portion through the skin. The external portion of the cochlear stimulator comprises a housing for electronics designed to accept a battery terminal. An external encased battery mounted to the terminal acceptor powers the cochlear stimulator. As such, the cochlear stimulator battery can be replaced easily by the patient and without the need for a surgical procedure. Because these batteries typically have a life of only three to twelve hours before they need to be recharged, the batteries may be detached and reattached one to several times a day. Furthermore, these devices are often worn by children and the elderly. Therefore, their battery connection must be both easy to work and robust.
A particular problem associated with cochlear stimulators is battery terminal corrosion. When sweat, bodily fluids and other contaminants come in contact with the battery terminal, corrosion occurs that eventually disables the cochlear stimulator. In some designs, the battery and electronics, including a transmitter, are located in a single housing that may be worn on a belt. In other designs, the batteries and electronics are in two separate housings, and the entire external portion of the cochlear stimulator is worn behind the ear, greatly increasing the exposure to sweat. Further, because cochlear stimulators typically require high voltages, often from lithium ion batteries, corrosion of the battery terminal connection is accelerated1. As such, an effective, efficient solution is needed for this problem. To date, no such solution has been found. 1 Indeed, zinc-based batteries of 1.5 volts have now been replaced with lithium ion batteries of 4 volts and greater. 
For example, one attempt to remedy corrosion is the use of gold plated, platinum plated or iridium plated battery terminals. These types of battery terminals are designed to better withstand corrosion. However, this approach is expensive and will only delay corrosion, not prevent it. Another approach is to incorporate a sacrificial electrode, often of zinc construction, to offset the corrosive effect. Once again, incorporating an additional electrode is costly and inefficient, and in any case, will not prevent corrosion after prolonged use and exposure to contaminants.
Other attempted remedies similarly fail to address the current needs. For example, the reference to Oehrlein et al., U.S. Pat. No. 4,207,390, designed primarily for automotive batteries, is limited to battery side terminal assemblies. This reference discloses a sealing means (in one embodiment an o-ring) that prevents electrolyte from reaching the battery side terminals. As such, a complete seal is not disclosed, but rather, a protection means limited to only the terminal area of a battery. Further, this reference incorporates numerous and intricate elements such as a female threaded connector, a lug, a collar, a head portion with recessed portion, a sealing means, a base portion having a series of keys, and a depending skirt. Naturally, the failure of any of these elements or their respective interconnection would result in leakage. Thus, this attempted remedy is costly, impractical and difficult to maintain.
The reference to Brander et al., U.S. Pat. No. 3,812,300, designed primarily to prevent sound leakage from a connection between a receiver and an acoustical load, discloses the use of solder joints in conjunction with an o-ring to complete the acoustical coupling rendering this reference impractical for use with modem cochlear devices. There is no teaching of a seal for preventing intrusion of bodily fluids. Similarly, the reference to Kraska et al., U.S. Pat. No. 4,010,760, incorporates an o-ring, however, the seal (which does not isolate the power source) further incorporates a screw tight fitting thereby missing the goal of simple removal.
The reference to Malek et al., U.S. Pat. No. 3,983,336, discloses the use of an o-ring, but principally for the purpose of facilitating rotation of the sound inlet passage of an outdated hearing aid. Similarly, the reference to Birch et al., U.S. Pat. No. 4,564,955, incorporates an o-ring, however, for the primary purpose of providing rotation friction to dispose the device in various positions. Furthermore, the seal in this reference does not provide a simplified solution to disconnect and connect the device components, nor does it provide an efficient means to change the o-ring after continued use.
Similar limitations are found in other U.S. references. For example, the reference to Fussell, U.S. Pat. No. 5,199,893, discloses a seismic connector for plugging geophones into a leader cable and having an o-ring, however, with the further limitations of a second recessed structure and a complicated and inaccessible connection means. The reference to Murakami, U.S. Pat. No. 6,102,739, incorporates the use of a resin chemical process to accomplish the seal which is wholly impractical for modem cochlear devices. Finally, the reference to Deutsch, U.S. Pat. No. 6,287,136 B1, discloses a complex connection means not appropriate to address present needs.
Turning to foreign references, the reference to Sanyo Electric Co. Ltd., Japan, JP7240198A2, discloses use of an o-ring to seal the terminal area of a battery used to power an electrical appliance. While far simpler than the Oehrlein et al. reference, the Sanyo reference provides little to no means of mechanically supporting the assembled battery and electric appliance. Designed for larger scale operations, the Sanyo reference is not practical for smaller scale operations such as wearable and/or implantable medical devices used in conjunction with lithium ion batteries.
Another reference to Sanyo Electric Co. Ltd., Japan, JP7272706A2, discloses a waterproof structure having a flange for a portable electric appliance. While the flange provides some mechanical support, this element is impractical to provide the support needed for a cochlear stimulator or like device. Similar limitations are found in the reference to Matsushita Electronic Ind. Co. Ltd., Japan, JP9237615A2, that discloses a device for providing liquid and air protection to a lead-acid battery.
The reference to Shin Kobe Electric Mach. Co. Ltd., Japan, JP7057719A2, discloses a battery terminal sealing part in which an o-ring is eliminated, for lead-acid battery terminals. Two other references to Shin Kobe Electric Mach. Co. Ltd., Japan, JP61114466A2 and JP60138847A2, disclose sealing parts limited to cylindrical batteries. Also, the complexities implicated in the Shin Kobe references, such as a movable o-ring, render them inefficient and impractical for medical devices.
Nor is the reference to Nippondenso Co. Ltd., Japan, JP5101731A2, disclosing a connecting terminal, practical for medical applications. While water resistance and insulation is provided by this reference, the lack of mechanical support for devices connected to the battery terminal renders this reference inappropriate for miniature, wearable and/or implanted devices.
Other references similarly fail to address current needs in medical device battery technology. The reference to Yuasa Battery Co. Ltd., Japan, JP62139245A2, discloses a sealing method for a storage battery. However, the use of setting resins renders this reference impractical for removable batteries used in conjunction with medical devices.
The reference to Furukawa Battery Co. Ltd., The Honda Motor Co. Ltd., Japan, JP60068552A2, discloses a sealing device for a storage battery terminal. While this reference may provide some level of insulation and sealing, its primary goal is to address shock and vibration.
Many of the electrical connection sealing mechanisms in the prior art lack the ability to provide mechanical support and require additional means to provide necessary mechanical support to render such mechanisms practical for use between a medical device and battery unit. Other inventions address the need for mechanical support; however, the manner of achieving such support is often needlessly complicated and impractical. Indeed, the means for supporting implantable medical devices proposed in the prior art generally require adjustments, in some cases requiring a physician or other medical practitioner to replace the battery unit. These limitations are both expensive and inconvenient.
A number of implantable devices use seals of some type to prevent blood leakage into the device; however, these inventions are not meant for frequent attachment and detachment, particularly by the patient. Two implantable devices that use seals are the cardiac pacemaker and defibrillator in which a header is permanently affixed to a hermetically sealed housing that contains the battery and electronics, which includes a microprocessor and timing circuitry. Flexible lead connectors are inserted into connector ports in the header, with the electrodes extending into or about the patient's heart. Seals may be provided, located on the lead connectors, within the connector ports, or both, to seal the device against intrusion by bodily fluids. The leads are attached by the surgeon at implant, usually via set screws, and then left in place for the life of the device, typically five to ten years or more. When the battery is depleted, the device is surgically accessed, the set screws are loosened, and the flexible leads are unplugged from the device and reconnected to a new device. Examples of such devices include those described in U.S. Pat. No. 6,327,502 B1 to Johansson et al., U.S. Pat. No. 6,039,685 to Bushek, U.S. Pat. No. 5,669,790 to Carson et al., and U.S. Pat. No. 5,919,215 to Wiklund et al.
Because various sizes and configurations of leads are available for cardiac pacemakers and defibrillators, implantable adaptors have become available to allow the pacemakers and defibrillators to be used with various leads having different connectors. These adaptors are detachably connectable to the header of the device on one side and to the leads on the other side. However, neither the adaptor-to-device connection nor the adaptor-to-leads connection is designed to be detached by the patient on a daily basis. Examples of such devices include U.S. Pat. No. 5,679,026 to Fain et al. and U.S. Pat. No. 6,006,135 to et al. To mechanically connect the adaptor to the device and the leads to the adaptor, Fain et al. uses set screws, requiring a hex wrench to loosen and tighten, which would be too difficult and time consuming for use in the present application. Kast et al. describes several connection devices, including a latching assembly, which requires a hex wrench to remove, and complex spring clip assemblies that are likely to fail if used daily.
The prior art includes implantable medical devices that have replaceable batteries; examples are found in U.S. Pat. No. 5,314,451 to Mulier and U.S. Pat. No. 5,411,538 to Lin. While mechanical support means are disclosed in these references, the support means are relatively complex and cumbersome to use and are not intended for daily disconnection and reconnection. In Mulier, the mechanical support means requires at least two securing locations, namely, the location of the electrical connector(s) and the location of a pin. With such a configuration, the requirement of at least two distinct securing locations needlessly complicates the manufacturing of this device and adds to the overall cost. Second, because the electrical connector is positioned far from the pin, removal of the battery unit is cumbersome in that both ends of the battery unit must be pulled out simultaneously and with equal force to avoid misalignment jams. Misalignment can also result in the breaking of an electrical connector or pin. In both Mulier and Lin, using four set screws, cap screws, or Sidelock™ connectors renders the removal and replacement of a battery time consuming and impractical if done daily for recharging. The patient who does not have sufficient manual dexterity to use small tools will be precluded from replacing the battery without outside help. Furthermore, the grommets, or septa, used to access the set screws may be prepierced or pierceable with a screwdriver, and may be self-sealing or may require sealing with room temperature vulcanizing (RTV) adhesive. The grommets themselves present potential leakage paths, and if penetrated daily, would quickly wear out. Replacing the grommets would require sending the unit to a lab or manufacturing facility. These problems severely limit the practicality and usefulness of the inventions of Mulier and Lin in an application that requires frequent detachment and reattachment of the battery. Lastly, the inventions of Mulier and Lin are intended for implant, and therefore, like the other implantable devices described above, use expensive implantable materials. As such, it is desirable to have a device that provides a simple, inexpensive, reliable, robust connection and sealing mechanism and that addresses the problems found in the prior art in an efficient and effective manner. However, and in view of the foregoing, nothing in the prior art addresses these deficiencies.